Embodiments of the inventive subject matter generally relate to the field of communication systems and, more particularly, to selecting antennas from an array of antennas for use in multi-user multiple-input multiple-output data transmissions.
Multi-user multiple-input multiple-output (MU MIMO) data transmissions are described in some IEEE 802.11 draft specifications (e.g., IEEE 802.11ac). In brief, multiple data streams are transmitted from an Access Point (AP) to two or more stations (STAs) contemporaneously. For example, beamforming can be used to transmit a first data stream from the AP to a first STA and a second data stream from the AP to a second STA at approximately the same time. Some APs can include an array of antennas that can be used to transmit and/or receive wireless signals to and from the STAs. Beamforming techniques can be used to formulate multiple signals for transmission through multiple antennas to a STA. A beam of data is formed to the STA as the multiple signals constructively and destructively interfere with each other. MIMO techniques can also take advantage of multipath interference to increase data throughput by using additional pathways defined by the multipath interference. Although beamforming is relatively well understood, selecting antennas from the antenna array, particularly for use in MU MIMO data transmissions, can be less straightforward.